Metal oxide free fluoroelastomer fusing member containing same

ABSTRACT

A fluoroelastomer composition free of metal or metal containing compounds, such as metal, metal alloys, metal salts or metal oxide suitable for the upper layer of a fuser roll which does not require the use of mercapto functional active release agents to prevent offset is provided. The fluoroelastomer compositions contain at least 23.4 mole percent hexafluoropropylene. They can be cured by electron beam treatment, fugitive base treatment or by the use of blocked/hindered bases.

This is a divisional of application Ser. No. 08/887,454, filed May 22,1992 now abandoned.

BACKGROUND OF THE INVENTION

The invention relates generally to metal oxide free fluoroelastomercompositions and to a fusing member having an outer layer of thefluoroelastomer for applying heat and pressure to fix toner particles torecording paper.

A fuser roll is a roller designed to apply direct heat and pressure to atoner image. The fluoroelastomer surface permits toner to be fixed tothe recording paper without adhering to the roller surface and canwithstand continuous exposure to high temperatures, silicone oils,toners, toner additives and paper product residue without unacceptablephysical degradation.

In general, when forming images by xerographic processes, an imageformed of a heat fusible toner powder is selectively disposed on aweb-like surface of a recording medium, such as paper, by electrostaticforces. Toner powders are commonly formed of a mixture of thermoplasticand/or thermosetting resin carriers and additives such as amorphouscarbon and magnetic particles. They are conventionally fixed to therecording paper by direct contact with a fuser roll which appliespressure and heat at temperatures between about 200° to 400° F.

The fusing process is conventionally accomplished by feeding a recordingmedium having the toner image thereon between the nip where two matedrollers meet. One or both of the rollers are heated, typically by aninternal heat source within the roller, so that the surface temperatureof the roller will be above the softening point of the resinous carrierof the toner.

The recording medium with the toner image thereon is fed between the tworollers which press towards each other to apply direct heat and pressureto the toner image. The amount of pressure and the length of time thatthe toner is heated determines the degree of fusing. The actualtemperature range suitable for fixing toner images to recording paper isreferred to as the "fusing window". The fusing window, TW can be definedby the formula:

    TW=T.sub.OFF -T.sub.MIN

wherein T_(OFF) is the Hot Offset temperature and T_(MIN) is the minimumfusing temperature. Hot Offset temperature is the temperature at whichthe cohesive forces within the molten toner layer are less than theadhesive forces between the toner and roll surface so that toner adheresto the fuser roll. T_(MIN) is the minimum temperature at which toner canbe acceptably fixed to the recording paper. This temperature range isdependent on the raw materials, type of toner, release agents and thepressure applied by the roller. It is important that the toner is fixedwithout "offset" occurring, in order to produce copies of acceptablequality. For commercial applications, a fusing window of at least 30° F.is acceptable for some applications. However, it is preferable to haveas large a fusing window as possible. Thus, a 60° F. fusing window isdesirable and a 100° F. fusing window is particularly ideal.

Conventional fusing systems have drawbacks. Softened toner generally hasan affinity for the surface of the fuser roll it contacts. When toneradheres to the surface of a fuser roll, it can unintentionally bedeposited on an unselected portion of the recording medium during thenext rotation of the roll. This phenomenon is referred to as offset.

To prevent offset, a thin coating of a release agent such aspolysiloxane fluid is commonly spread over the surface of the fuser rollwhich contacts the surface of the toner image. The polysiloxane fluidreduces the surface free energy of the roll surface and decreases theaffinity of the toner for the roll. Surface tension values for severalconventional fuser roll materials are set forth below in Table I.

                  TABLE I                                                         ______________________________________                                        Surface Tension of Fuser Roll Materials                                       Fuser Roll Surface  Surface Tension nMn                                       ______________________________________                                        Polytetrafluoroethylene (PTFE)                                                                    18.0-18.5                                                 Polyvinylidene fluoride (PVF.sub.2)                                                               21-22                                                     Polysiloxane Compounds                                                                            28-29                                                     Polyfluorocarbon Elastomers                                                                       35-37                                                     Polysiloxane Release Agents                                                                       19-21                                                     ______________________________________                                    

When compounding or formulating fluorocarbon elastomers, metal oxidesare typically included to act as an acid accepter, cure activator,reinforcing filler and/or as an additive to promote improved chemicalresistance. It is believed that every commercially available fuser rollhaving a fluoroelastomer surface contains metal oxide particles in atleast the fluoroelastomer surface layer. U.S. Pat. Nos. 4,257,699,4,264,181 and 4,272,179 describe fuser rolls in which additional metaloxide filler particles are added to the fluoroelastomer surface materialto increase the metal oxide content of the surface of the fuser rollsbeyond that needed to promote cure of the material. Fluoroelastomersdescribed in U.S. Pat. No. 5,035,950 contain only so much metal oxide asis necessary to effect cure of the high fluorine content material.

These patents describe that use of a polymer release agent havingmercapto functional groups applied to the surface of a fuser roll havingmetal oxide filler decreases problems associated with offset. When themetal-containing filler in the elastomer surface layer is present insufficient amount, it interacts with the polymeric release agent toproduce an active release film. This active release film prevents thethermoplastic resin toner from contacting the elastomeric materialitself and accordingly, offset is avoided.

Although this active release construction has proven to be commerciallyacceptable, it nevertheless has drawbacks. Release agent fluids havingmercapto functional groups are expensive. They can also present anunpleasant odor in the office environment and interfere with the abilityto write or type on the copy sheet.

Accordingly, it is desirable to provide an improved fusing system whichovercomes the shortcomings of the conventional fuser systems describedabove.

SUMMARY OF THE INVENTION

Generally speaking, in accordance with the invention, fluoroelastomercompositions free of metal or metal containing compounds, such as metalsor metal oxides, which are particularly well suited for the topcoat of afusing member for applying heat and pressure to fix toner to a recordingmedium are provided. The fluoroelastomer composition can be cured byelectron beam treatment, fugitive base treatment or the use ofblocked/hindered amines. A fusing member having metal freefluoroelastomer surfaces have advantages over conventional fusingmembers because they do not require the use of expensive mercaptofunctional active release agents to prevent offset.

Accordingly, it is an object of the invention to provide an improvedfluoroelastomer composition free of metal or metal containing compounds,such as metal oxides.

Another object of the invention is to provide an improved fuser rollhaving a topcoat of fluoroelastomer free of metal or metal containingcompounds for fixing toner to a recording medium.

A further object of the invention is to provide a fuser roll having ametal or metal containing compound free fluoroelastomer topcoat forfusing without the need to use mercapto functional release agents.

Still other objects and advantages of the invention will in part beobvious and will in part be apparent from the specification anddrawings.

The invention accordingly comprises the several steps and the relationof one or more of such steps with respect to each of the others, and thecomposition possessing the features, properties and the relation ofconstituents and the article possessing the features, properties, andthe relation of elements, which are all exemplified in the followingdetailed disclosure, and the scope of the invention will be indicated inthe claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the invention, reference is had to thefollowing description taken in connection with the accompanyingdrawings, in which:

FIG. 1 is a schematic cross-sectional view of a fuser roll testassembly;

FIG. 2 is a cross-sectional view of a single layer fuser rollconstructed in accordance with an embodiment of the invention; and

FIG. 3 is a cross-sectional view of a multi-layer fuser roll constructedin accordance with another embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A fusing member constructed in accordance with an embodiment of theinvention includes a fluoroelastomer topcoat surface that issubstantially free of metal and metal containing compounds, such asmetal or metal oxide particles. The fusing member can be a belt, a flatsurface or another substrate having suitable shape for fixing tonerimages to a recording medium, such as paper, at elevated temperaturesunder pressure. A preferred fusing member is a fuser roll having a metalcore that can be hollow, covered with the fluoroelastomer material. Aheating element can be included within the metal core to heat thefluoroelastomer surface. The fuser roll can be used to fix toner powderto a recording medium, such as paper, without offset and without relyingon the interaction between metal oxides and mercapto functional releaseagent fluids.

The outer layer of the fusing member is of a fluoroelastomer compositionhaving a greater molar content of hexafluoropropylene (HFP) thanconventional fluoroelastomers. The fluoroelastomer compositions preparedin accordance with the invention include more than about 23.4 mole % HFPand more preferably more than about 30.0 mole % HFP. A preferredcomposition is a copolymer of vinylidene fluoride (VF₂) andhexafluoropropylene (HFP) that includes more than about 69% totalfluorine by weight, preferably 69 to 71% fluorine by weight. It ispreferable to include as much HFP as is practical. The molar ratio ofVF₂ to HFP is preferably less than 2 and more preferably about 1.7 orless. An acceptable preferred range is between 1.25 and 1.75.

The fluoroelastomer composition can also include cure additives, such ashexafluoropropylidine diphenol, triphenyl benzyl phosphoniumchloride/bromide and acid acceptors (though not metal oxides). Theeffectiveness of including higher amounts of HFP than is conventionalrelates to the associated reduction in surface energy at the expense ofother properties conventionally considered to be more important.

Fuser rolls having a fluoroelastomer surface substantially free of metalcontaining compounds such as metal oxides can be cured by severalmethods. Crosslinking can be induced by using diamines, a combination ofdiamines and bisphenol or by other organic base treatments such asammonia vapor deposition. Another method involves the use of radiationcuring such as electron beam treatment. Such techniques are known forthe use of curing various polymer systems, but are uniformly notemployed in the production of commercially available fuser rolls, wherethe mechanical properties of polymers having metal oxide particlestherein has been the accepted material of choice. Base treatmentincludes the use of blocked/hindered amines, "fugitive" bases which willleave the polymer system after attack on the polymer material to yieldunsaturation sites and electron beam treatment. The fugitive basetreatment can be conducted in the vapor or liquid phases.

Metal oxide free curing can be accomplished with treatment byblocked/hindered amines. These include DIAK 3 (N, N'-D- Cinnamylidene-1,6-hexanediamine and DIAK 1 (hexamethylene - diaminecarbamate) which arecommercially available curing agents sold by DuPont of Wilmington, Del.This type of curing is described in Example 1.

Electron beam processing and methods for estimating the requiredspecifications of the electron accelerator are discussed in Becker, R.C., "Accelerator Requirements For Electron Beam Processing", Radiat.Phys. Chem., vol 14, Pages 353-375 (1975), the contents of which areincorporated herein by reference.

Typically, the fuser roll is conveyed into a chamber where it isbombarded by a highly energetic beam of electrons. Curing occurs duringthe brief interval during which the fuser roll is exposed to theelectron beam, which is spread over the entire surface.

Additional details regarding electron beam processing can be obtainedfrom Radiation Dynamics, Inc., 151 Hartland Blvd., Edgewood, N.Y. 11717.See also Cleland, M. R., et al., "High Powered DC ElectronicAccelerators For Industrial Applications", RDI Technical InformationSeries TIS 79-6 presented at the 3rd All-Union Conference on a partaccelerators, Leningrad, USSR, Jun. 26-28, 1979, the contents of whichare incorporated herein by reference. Still further details can be foundin Bly, J. H. "Radiation Curing of Elastomers" presented at theEducation Symposium of a meeting of the Rubber Division, AmericanChemical Society, Philadelphia, Pa., May 3-6, 1982.

The curing of elastomeric material by Electron Beam (EB) radiationgenerates carbon-carbon bonds between molecules without using cureagents such as metal oxide powders. Compounding for the electron beam issimilar to that for other curing processes. Commercial applications arewell developed in the manufacture of wire and cable, rubber tires, heatshrink products and others. However, it is believed that this techniquehas never been applied to curing polymer materials for fuser rolls inthe absence of conventional care system including the use of metaloxides.

Electron Beam (EB) dosages of 1-40 megarads are acceptable for manyapplications; 3-40 MRads is preferred and 5-20 MRads is more preferred.It is useful to include cross linking aids (co-agents) in the polymercomposition at concentrations of about 1-10 parts by weight per 100parts polymer. EB crosslinkable di or poly functional oligimers include:1,6- Hexanediol Diacrylate, Trimethylol Propane Triacrylate, Bisphenol AExpoxy Diacrylate (EBECRYL 3700), TAC (2,4,6- Tris (Allyloxy) - S - Tri-azine and TAIC (Triallylisocyanurate).

A fuser roll test assembly 100 is shown generally in FIG. 1 and appliesheat and pressure to fuse a quantity of toner particles 12 on a sheet ofpaper 13 between a fuser roll 20 and a pressure roll 30. Fuser roll testassembly 100 also includes a release agent application unit 11 includinga wick 15 for applying release agent to the surface of fuser roll 20. Astripper finger 16 facilitates the separation of paper 13 from roll 20.

FIG. 2 is a cross-sectional view of a fuser roll 200 constructed inaccordance with an embodiment of the invention. Fuser roll 200 includesa hollow middle core 201 covered with a fluoroelastomer surface layer202. A second fuser roll 300 is shown in cross-sectional view in FIG. 3.Fuser roll 300 includes an insert 302 covered with a base coat 303having a tie coat 304 disposed thereon and a topcoat 302 disposed on tiecoat 304. Base coat 303 is preferably 0.5 to 5 mil thick and the overallcoating (either surface layer 202 or combined layers 303, 304, and 302)should be about 3-8 mils thick.

The following Examples describe metal and metal oxide freefluoroelastomer compositions and fuser rolls having a topcoat of thecomposition prepared in accordance with the invention. These examplesare presented for purposes of illustration only, and are not intended tobe construed in a limiting sense.

EXAMPLE 1

A series of conventional fluoroelastomer compositions and metal oxidefree fluoroelastomer compositions in accordance with the invention weremade. The fluoroelastomer topcoat composition of five conventional fuserrolls having metal oxide therein (A-E) and two metal oxide freefluoroelastomer topcoat fuser rolls in accordance with the invention (Fand G) are shown below in Table II. Compositions A through D containmetal oxide filler conventionally used to promote interaction with amercapto functional release agent. Composition E contains no more thansufficient residual metal oxide to act as an activator and acid accepterfor conventional cross-linking of the composition, but insufficientamount to react effectively with a mercapto functional release agent.

The seven compositions A through G were prepared by mixing thecomponents with a two roll mixing mill. The polymer was loaded betweenthe two mill rolls to obtain a "bank". Cross-blending was obtained bycutting sheets off the mill roll until a uniform viscosity is achieved.The powdered ingredients were then added over the polymer bank anddispersed therein by cutting and cross-blending. The curatives are thenadded and the composition was cut and cross-blended to obtain thoroughand uniform dispersion of all ingredients. The resulting material wascooled in the air, compound tested then used as the surface material fora fuser roll. The components can also be mixed with an internal mixerdevice known in the trade as a Banbury. When the fuser roller materialis formed using a liquid state composition, the components can beeffectively prepared by "in-situ" mixing techniques. In-situ mixinginvolves dissolving the polymer in a solvent, then adding the powderedingredients including the activator and curatives. In compositionshaving a tendency to gel rapidly, it is preferable to employ a two orthree component system to isolate the calcium hydroxide and/or theacceptor.

In compounding or formulating fluorocarbon elastomers, metal oxides areconventionally added to act as an acid acceptor, cure activator,reinforcent filler and/or at times as an additive to promote improvedchemical resistance. The use of lead oxide, for example, improves thesteam and acid resistance of fluoroelastomer compounds and is well knownin the art. Metal fillers are also added to provide actual release byinteraction with mercapto functional compounds. However, it has beendetermined that metal and metal oxide free compositions provideadvantages as a top coat surface in a fuser roll despite the diminishedmechanical properties.

                                      TABLE II                                    __________________________________________________________________________    Fuser Roll Surface Material Compositions                                                   COMPARISON METAL OXIDE CONTAING    METAL OXIDE FREE                           FLUOROELASTOMER COMPOSITION        FLUOROELASTOMER               Composition  A      B      C      D      E      F       G                     __________________________________________________________________________    Fluorel 2530 x      x      x      x      100    100     x                     (copolymer of VF.sub.2 and                                                    HFP)                                                                          L12176       x      x      x      x      x      x       100                   (copolymer VF.sub.2 and HFP)                                                  Terpolymer VF.sub.2 HFP                                                                    100    x      x      x      x      x       x                     & TPE                                                                         Copolymer VF.sub.2 & TPE                                                                   x      100    x      100    x      x       x                     Terpolymer VF.sub.2, HFP                                                                   x      x      100    x      x      x       x                     & TPE & Cure Site                                                             Monomer                                                                       Cupric Oxide x      x      15     15     x      x       x                     Lead Oxide   15     15     x      x      x      x       x                     Magnesium Oxide                                                                            x      x      2.0    3      3      x       x                     Calcium Hydroxide                                                                          x      x      1.0    6      6      x       x                     Curative 20  2.5    1.4    x      1.4    x      x       x                     Curative 30  3.5    2.8    x      2.0    x      x       x                     Curative 50  x      x      5.0    x      x      x       x                     DIAK No. 3   x      x      x      x      x      6.0     6.0                   Polymer Data Terpolymer                                                                           Copolymer                                                                            Tetrapolymer                                                                         Copolymer                                                                            Copolymer                                                                            Copolymer                                                                             Copolymer                          of VF.sub.2 HFP                                                                      of VF.sub.2 &                                                                        of VF.sub.2, HFP,                                                                    of VF.sub.2 &                                                                        of VF.sub.2 and                                                                      of VF.sub.2                                                                           of VF.sub.2 and                    & TPE  HFP    TPE & cure                                                                           HFP    HFP    HFP     HFP                                              site monomer                                       Total Fluorine (wt. %)                                                                     68.5   66%    69.0%  66%    69.6%  69.6%   70                    HFP Content (molar %)                                                                      18     21     22     21     37     37      44                    VF.sub.2 Content (molar %)                                                                 61     79     55     79     63     63      56                    TFE Content (molar %)                                                                      21     x      23     x      x      x       x                     VF.sub.2 /HFP Ratio (molar)                                                                3.39   3.76   2.5    3.76   1.70   1.70    1.27                  __________________________________________________________________________

    ______________________________________                                        INGREDIENT DATA                                                               CHEMICAL                      MANU-                                           COMPOSITION     TRADE NAME    FACTURER                                        ______________________________________                                        Terpolymer of VF.sub.2, HFP                                                                   Viton B-50, Fluorel,                                                                        DuPont, 3M                                      & TPE with 68.5%                                                                              FT 2430                                                       flourine                                                                      Copolymer of VF.sub.2 and                                                                     Viton E-45, Fluorel,                                                                        DuPont, 3M                                      HFP with 65.9% fluorine                                                                       FC 2145                                                       Copolymer of VF.sub.2, HFP                                                                    Viton E-60, Fluorel,                                                                        DuPont, 3M                                      with 66% fluorine                                                                             FC 2230                                                       Tetrapolymer of FV.sub.2 and                                                                  Viton GF, Fluorel,                                                                          DuPont, 3M                                      HFP TFE and cure site                                                                         FLS 2690                                                      monomer with 69%                                                              fluorine                                                                      Copolymer of VF.sub.2 and                                                                     FC 2530       3M                                              HFP containing                                                                phosphonium salt                                                              accelerator and                                                               bisphenol crosslinker                                                         with 69.6% fluorine                                                           33% dispersion of                                                                             Curative 20   DuPont                                          organophosphonium salt                                                        in Viton E-45                                                                 50% dispersion of                                                                             Curative 30   DuPont                                          bisphenol (dihyroxy                                                           aromatic compound) in                                                         Viton E-45                                                                    Proprietary accelerator                                                                       Curative 50   DuPont                                          and bisphenol curative                                                        system                                                                        Copolymer of VF.sub.2 and HFP                                                                 L-12176       3M                                              containing phosphonium                                                        salt accelerator and                                                          bisphenol crosslinker                                                         with 70% fluorine                                                             N, N'-Di-cinnamylidene-                                                                       DIAK No. 3    DuPont                                          1, 6, hexanediamine                                                           ______________________________________                                    

Fuser roll samples were formed by covering a 1.5 inch standard aluminuminsert with a 4 mil thick fluoroelastomer base coat covered with a 2 milthick topcoat of the materials shown below in Table III. The samplefuser rolls were prepared by first mixing the base coat material andtopcoat material in a two roll mixing mill. The base coat compound wasformulated by combining 100 parts VITON E-60 (DuPont) fluoroelastomer,30 parts thermal carbon black filler, 12 parts magnesium oxide (as anactivator/acid accepter) and 5.5 parts blend CURATIVE 20 (DuPont) andCURATIVE 30 (DuPont).

The mixed starting materials were dissolved in a 50:50 blend of methylethyl ketone (MEK) and methyl isobutyl ketone (MIBK) solvents toapproximately a 15% solid concentration. The aluminum insert wasprecured with a primer layer of THIXON 300/301 adhesive and then sprayedwith the base coat solution to a thickness of about 5-6 mils. The coatedsample was maintained at room temperature to permit residual solvent toevaporate and then cured in a circulating oven for up to 24 hours at atemperature of 150° to 450° F. The sample was then ground to a base coatthickness of 3-4 mils. After washing the sample with solvent, it wasover sprayed with a 15% solid topcoat solution to yield a coating havinga thickness of 4 to 5 mils. Residual solvent was permitted to evaporateand the sample was subjected to final curing in a hot air circulatingoven for up to 24 hours at 450° F. The topcoat was then ground to athickness of 2 to 3 mils.

Fusing tests herein were carried out by passing an 8.5×11.5 inch 75 g/m²sheet of paper having toner particles thereon between fuser roll 20 andpressure roll 30 to fuse toner 12 to paper 13. Fuser roll life isindicated by the number of sheets of paper that can be successfullyfused before failure by either offset, mechanical failure or some otherdifficulty. Fuser rolls including metal free compositions F and G fromTable II were found to be acceptable.

The above procedure was followed for each of the following Runs 1-5,except that the topcoat composition was changed as set forth in TableIII and the insert was a standard two inch insert. Fuser roll samplesproduced from Runs 1, 2, 3 and 5 were installed and tested in a Xerox1065 copier. The results of each copy life test are shown in Table IV,which demonstrates the advantages of a high fluorine content and metaloxide free fluoroelastomer composition for fusing application.

                  TABLE III                                                       ______________________________________                                        FORMULATION OF TOPCOAT COMPOSITION                                                          RUN NUMBERS                                                     INGREDIENTS     1      2       3    4     5                                   ______________________________________                                        FC 2145 (66% F) 100    x       x    100   x                                   L 12176 (70% F) x      100     100  x     100                                 MAGNESIUM OXIDE 2      2       2    x     x                                   CALCIUM HYDROXIDE                                                                             4      4       4    X     x                                   DIAK No. 3      x      x       x    6     6                                   CURATIVE 20     1.4    x       x    x     x                                   CURATIVE 30     2.8    x       x    x     x                                   ______________________________________                                         FC 2145  Copolymer of VF.sub.2 and HFP containing 66% total fluorine by       weight and a VF.sub.2 /HFP molar ratio of 3.76                                FC 2530  Copolymer of VF.sub.2 and HFP containing 69% total fluorine by       weight and a VF.sub.2 /HFP molar ratio of 1.70; contains phosphonium salt     accelerator and bisphenol crosslinker.                                        L12176  Copolymer of VF.sub.2 and HFP containing 70% total fluorine by        weight and a VF.sub.2 /HFP molar ratio of 1.27; contains phosphonium salt     accelerator and bisphenol crosslinker.                                        DIAK NO. 3  N, N.sup.1 -Dicinnamylidene  1, 6 Hexanediamine                   CURATIVE 20  33% dispersion of organophophonium salt in Viton E45             CURATIVE 30  50% dispersion of bisphenol (dihydroxy aromatic compound) in     Viton E45                                                                

A comparison was made in Table IV below between fuser rolls having thecompositions of Runs 1, 2, 3 and 5.

                  TABLE IV                                                        ______________________________________                                                          Roll Life                                                   Material          Type Release Agent                                          Description       Non-Functional                                              Run #             Polydimethysiloxane                                         ______________________________________                                        1 - 66% F with metal oxide                                                                       6,000                                                      2 - 69% F with metal oxide                                                                      12,000                                                      3 - 70% F with metal oxide                                                                      21,000                                                      5 - 70% F no metal oxide                                                                        115,000                                                     ______________________________________                                    

By comparing Examples 1 and 2, it can be seen that including a high HFPpercentage is associated with 100% increase in roll life. Example 3having 70% F shows a 75% increase in roll life compared to Example 2 anda 250% increase over Example 1 with 66% F. However, the most dramaticresults can be seen by comparing Examples 3 and 5. The elimination ofmetal oxide within the fuser roll surface material led to a 450%increase in roll life of 94,000 copies. Accordingly, it is preferred toprovide a fuser roll without any metal oxide in the material.

During conventional cross-linking, metal oxides are used to generateunsaturation in the polymer material. However, the reaction is generallynot easy to control and accordingly, it is has been common to employexcess metal oxides to achieve acceptable results. However, thistypically generates excess unsaturation. The unsaturation in the curedpolymer material increases the surface energy and may decrease fuserroll life before offset occurs. The metal particles at the roll surfacealso increase the surface energy.

It has been discovered that by carefully controlling the curing ofmetal-oxide free polymer material, sufficient cross-linking is achievedto cure the polymer and also provide acceptable mechanical properties,without creating excessive unsaturation and without any residualmaterial to increase the surface energy of the fuser roll. Metal freecompositions in accordance with the invention include sufficient sitesfor cross-linking, but not excessive sites which would oxidize, therebyincreasing surface energy and impede toner release. Furthermore, withoutresidual metal oxide particles, the composition will inherently yield apolymer surface having lower surface energy particularly well suited forfusing applications.

EXAMPLE 2

A fuser roll is prepared in accordance with Example 1, employing L-12176as the surface material, which is sprayed onto a procured base layerhaving a 4 mil thickness. The surface material is air dried and thenpositioned in an electron beam apparatus curing device and exposed to anenergy dose of 15 MRad. The resultant fuser roll will perform acceptablywith polydimethylsiloxane release fluid having a viscosity of about 500CSTKS and will exhibit excellent roll life and release properties,including adequate release at a temperature of about 185° C.

EXAMPLE 3

A fuser roll is prepared as in Example 2, except that the top coatmaterial is formed of 100 parts L-12176 together with five parts EBECRYL3700. EBECRYL 3700 (available from RADCURE of Louisville Ky.) is aconventional metal-oxide free cross-linking aid (co-agent) that has beenfound to improve the efficiency of electrons beam cures. The roll iscured with an electron beam dosage of about 5 MRad's and will performsimilarly to the roll of Example 2.

EXAMPLE 4

Curing without metal oxides can also be effected by treatment with abase in either the vapor or liquid phase. For example, ammonia,methylamine, ethylamine and dimethylamine gas can be passed over a fuserroll coated with metal oxide free fluoroelastomer material. The basewill attack the polymer chain and create unsaturated sites forcross-linking. Subsequent heat treatment will cure the material andprovide a fuser roll surface having exceptional release properties thatdoes not require interaction with a mercapto functional release agent.

Base treatment as described herein can also be accomplished in theliquid phase. The above-noted gaseous materials can be solved in asuitable solvent, such as ether or alcohols and the uncured fuser rollcan be completely immersed therein. Propyl and butyl amines can also beemployed, as well as combinations of the above bases.

EXAMPLE 5

A fuser roll is prepared as in Example 1, except that the surface layeris formed of L-12176 which is sprayed onto the precured base layer. Thesurface material is air dried and placed in a cylindrical stainlesssteel chamber equipped with a gas inlet and exhaust apparatus. A gaseousmixture of 5% anhydrous ammonia and 95% N₂ (by volume) is allowed toflow over the roll surface until sufficient unsaturation is developed ascan be evidenced by a change in surface color or through instrumentalanalysis. The roll is then removed and placed in a forced air oven at atemperature of about 200° C. for about 24 hours. It will perform wellwith a polydimethylsiloxane release fluid having a viscosity of 500 CSTKat surface temperatures of about 185° C.

EXAMPLE 6

A fuser roll is prepared as in Example 1, except that the surface layeris formed of Fluorel 2530 which is sprayed onto a precured base layer.The Fluorel layer is air dried and then placed in a cylindrical steelchamber equipped with gas inlets and outlets. A gaseous mixture of 5%anhydrous ammonia and 95% N₂ (by volume) is allowed to flow over theroll surface. The roll is then removed and placed in a forced air ovenat 200° C. for 24 hours. The roll will exhibit adequate release with a500 CSTK linear reactive polydimethylsilicone fluid copolymer containing0.1 wt % mercaptopropylmethylsiloxane modification at temperatures ofabout 185° C.

EXAMPLE 7

A fuser roll is prepared as in Example 1, except that the surface layeris formed of L-12176. The material is cured by immersing the fuser rollin a 10 wt % solution of butylamine in diethylether at 25° C. untilsurface discoloration is apparent. The roll is then removed from theamine-ether solution and washed with ethyl alcohol and distilled water.It is then heat treated at 200° C. for 24 hours. The roll will exhibitadequate release properties at temperatures of about 85° C. with a 500CSTK liner polysiloxane release fluid.

It will thus be seen that the objects set forth above, among those madeapparent from the preceding description, are efficiently attained and,since certain changes may be made in carrying out the above method, andin the composition and article set forth without departing from thespirit and scope of the invention, it is intended that all mattercontained in the above description and shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

It is also to be understood that the following claims are intended tocover all of the generic and specific features of the invention hereindescribed and all statements of the scope of the invention which, as amatter of language, might be said to fall therebetween.

Particularly it is to be understood that in said claims, ingredients orcompounds recited in the singular are intended to include compatiblemixtures of such ingredients wherever the sense permits.

What is claimed is:
 1. A fusing member for fixing toner particles to arecording medium, comprising a substrate and an outer layer offluoroelastomer material on the substrate, the outer layer offluoroelastomer material being a polymer including vinylidene fluorideand at least about 23.4 mole percent hexafluoropropylene and curedwithout the addition of metal containing material.
 2. The fusing memberof claim 1, wherein the member is a fuser roll.
 3. The fusing member ofclaim 1, wherein the fluoroelastomer includes at least about 30 molepercent hexafluoropropylene.
 4. The fusing member of claim 2, whereinthe fluoroelastomer is a copolymer of hexafluoropropylene (HFP) andvinylidene fluoride (VF₂).
 5. The fusing member of claim 4, wherein themolar ratio of VF₂ to HFP is less than
 2. 6. The fusing member of claim1, wherein the substrate is in the form of a metal core having a layerof silicone material including metal oxide material therein, disposed onthe metal core.
 7. The fusing member of claim 6, including a tie coat offluoroelastomer material between the surface layer and the siliconematerial.
 8. A fusing system for fusing toner to a recording medium,comprising a fuser roll having an outer surface formed offluoroelastomer material including vinylidene fluoride and at leastabout 23.4 mole percent hexafluropropylene cured without metalcontaining material and a polysiloxane release agent fluid disposed onthe surface of the fuser roll, the release agent substantially free ofmercapto functional compounds.
 9. The fusing system of claim 8, whereinthe fluoroelastomer includes at least 23.4 mole percenthexafluoropropylene.
 10. The fusing system of claim 8, wherein thefluoroelastomer includes at least 70% by weight fluorine.